[PATCH] Driver core: add generic "subsystem" link to all devices

Like the SUBSYTEM= key we find in the environment of the uevent, this
creates a generic "subsystem" link in sysfs for every device. Userspace
usually doesn't care at all if its a "class" or a "bus" device. This
provides an unified way to determine the subsytem of a device, regardless
of the way the driver core has created it.

Signed-off-by: Kay Sievers <kay.sievers@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 11 insertions, 2 deletions

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 64ba9011d1a8..050d86d0b872 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -374,6 +374,7 @@ int bus_add_device(struct device * dev)
                 error = device_add_attrs(bus, dev);
                 if (!error) {
                         sysfs_create_link(&bus->devices.kobj, &dev->kobj, dev->bus_id);
+                        sysfs_create_link(&dev->kobj, &dev->bus->subsys.kset.kobj, "subsystem");
                         sysfs_create_link(&dev->kobj, &dev->bus->subsys.kset.kobj, "bus");
                 }
         }
@@ -408,6 +409,7 @@ void bus_attach_device(struct device * dev)
 void bus_remove_device(struct device * dev)
 {
         if (dev->bus) {
+                sysfs_remove_link(&dev->kobj, "subsystem");
                 sysfs_remove_link(&dev->kobj, "bus");
                 sysfs_remove_link(&dev->bus->devices.kobj, dev->bus_id);
                 device_remove_attrs(dev->bus, dev);
diff --git a/drivers/base/class.c b/drivers/base/class.c
index 50e841a33af0..9aa127460262 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -561,6 +561,7 @@ int class_device_add(struct class_device *class_dev)
                 goto out2;
 
         /* add the needed attributes to this device */
+        sysfs_create_link(&class_dev->kobj, &parent_class->subsys.kset.kobj, "subsystem");
         class_dev->uevent_attr.attr.name = "uevent";
         class_dev->uevent_attr.attr.mode = S_IWUSR;
         class_dev->uevent_attr.attr.owner = parent_class->owner;
@@ -737,6 +738,7 @@ void class_device_del(struct class_device *class_dev)
                 sysfs_remove_link(&class_dev->kobj, "device");
                 sysfs_remove_link(&class_dev->dev->kobj, class_name);
         }
+        sysfs_remove_link(&class_dev->kobj, "subsystem");
         class_device_remove_file(class_dev, &class_dev->uevent_attr);
         if (class_dev->devt_attr)
                 class_device_remove_file(class_dev, class_dev->devt_attr);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 252cf403f891..cc8bb97427d0 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -319,9 +319,12 @@ int device_add(struct device *dev)
                 dev->devt_attr = attr;
         }
 
-        if (dev->class)
+        if (dev->class) {
+                sysfs_create_link(&dev->kobj, &dev->class->subsys.kset.kobj,
+                                  "subsystem");
                 sysfs_create_link(&dev->class->subsys.kset.kobj, &dev->kobj,
                                   dev->bus_id);
+        }
 
         if ((error = device_pm_add(dev)))
                 goto PMError;
@@ -422,8 +425,10 @@ void device_del(struct device * dev)
                 klist_del(&dev->knode_parent);
         if (dev->devt_attr)
                 device_remove_file(dev, dev->devt_attr);
-        if (dev->class)
+        if (dev->class) {
+                sysfs_remove_link(&dev->kobj, "subsystem");
                 sysfs_remove_link(&dev->class->subsys.kset.kobj, dev->bus_id);
+        }
         device_remove_file(dev, &dev->uevent_attr);
 
         /* Notify the platform of the removal, in case they